package cn.cht.sqlsession;

import cn.cht.pojo.Configuration;
import cn.cht.pojo.MappedStatement;
import cn.cht.sqlconfig.BoundSql;
import cn.cht.utils.GenericTokenParser;
import cn.cht.utils.ParameterMapping;
import cn.cht.utils.ParameterMappingTokenHandler;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class SimpleExecutor implements  Executor {

    //抽取公共方法       执行JDBC
    public int executeJDBC(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {
        // 1. 注册驱动，获取连接
        Connection connection = configuration.getDataSource().getConnection();

        // 2. 获取sql语句 : select * from user where id = #{id} and username = #{username}
        //转换sql语句： select * from user where id = ? and username = ? ，转换的过程中，还需要对#{}里面的值进行解析存储
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);

        // 3.获取预处理对象：preparedStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        // 4. 设置参数
        //获取到了参数的全路径
        String paramterType = mappedStatement.getParamterType();
        Class<?> paramtertypeClass = getClassType(paramterType);

        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();

            //反射
            Field declaredField = paramtertypeClass.getDeclaredField(content);
            //暴力访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);

            preparedStatement.setObject(i+1,o);

        }


        // 5. 执行sql
        int i = preparedStatement.executeUpdate();

        return i;
    }

    @Override
    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {

        // 1. 注册驱动，获取连接
        Connection connection = configuration.getDataSource().getConnection();

        // 2. 获取sql语句 : select * from user where id = #{id} and username = #{username}
        //转换sql语句： select * from user where id = ? and username = ? ，转换的过程中，还需要对#{}里面的值进行解析存储
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);

        // 3.获取预处理对象：preparedStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        // 4. 设置参数
        //获取到了参数的全路径
        String paramterType = mappedStatement.getParamterType();
        Class<?> paramtertypeClass = getClassType(paramterType);

        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();

            //反射
            Field declaredField = paramtertypeClass.getDeclaredField(content);
            //暴力访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);

            preparedStatement.setObject(i+1,o);

        }


        // 5. 执行sql
        ResultSet resultSet = preparedStatement.executeQuery();

        ArrayList<Object> arrayList = new ArrayList<>();
        //6.封装返回结果
        String resultType = mappedStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);

        while (resultSet.next()){
            //具体实现
            Object o = resultTypeClass.newInstance();
            //元数据
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i <=metaData.getColumnCount() ; i++) {
                //字段名
                String catalogName = metaData.getColumnName(i);
                //字段的值
                Object value = resultSet.getObject(catalogName);

                //使用反射 或者内省 ,根据数据库表和实体的对应关系 ,完成封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(catalogName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o,value);
            }
            arrayList.add(o);
        }
        return (List<E>) arrayList;
    }

    @Override
    public int addOne(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {
        return  executeJDBC(configuration, mappedStatement, params);

    }

    @Override
    public int update(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {
        return  executeJDBC(configuration, mappedStatement, params);
    }

    @Override
    public int delete(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {
        return  executeJDBC(configuration, mappedStatement, params);
    }

    /**
     * 根据路径获取对象
     * @param paramterType
     * @return
     */
    private Class<?> getClassType(String paramterType) throws ClassNotFoundException {
        if (paramterType != null){
            Class<?> aClass = Class.forName(paramterType);
            return aClass;
        }
        return null;
    }

    /**
     * 完成#{}的解析工作:1. 将#{} 转化为? 2. 解析成#{}里面的值,进行存储
     * @param sql
     * @return
     */
    private BoundSql getBoundSql(String sql) {
        //标记处理类:配置标记解析器来完成对占位符的解析处理工作
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        //标记解析器
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);
        String parseSql = genericTokenParser.parse(sql);
        //#{} 解析出来的参数名称
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();

        return new BoundSql(parseSql,parameterMappings);
    }
}
